Yannick Petit

• PhD (HDR) - Associate Professor
• Associate Professor at French National Centre for Scientific Research

Ionizing irradiation was performed on barium–germanium–gallium (BGG) glasses using a 2.5 MeV electron beam. Through electron spin resonance spectroscopy, paramagnetic point defects, such as germanium- and gallium-related electron and hole trap centers, have been identified. The presence of silver in the BGG glass appears to hinder the stability of...

Since its demonstration in 2017, laser-induced Type A modifications in silver-containing glasses have been exploited for fabricating waveguides, couplers, volume Bragg Gratings and, more recently, waveguides Bragg Gratings. Laser-induced silver-supported structures exhibit sub-diffraction characteristics being always associated with a positive refr...

Localized sub-micrometer-scale visible and near-IR fluorescence structures have been achieved in threedimension (3D) thanks to femtosecond laser-activated photochemistry of Bismuth in a Bismuth-doped phosphate glass. These structures exhibit high fluorescence contrast with good spatial resolution with spectral emission in the red and near-IR ranges...

We present Type-A volume Bragg gratings inscribed within minutes using a 100 W laser in burst mode and the phase-mask approach. This surpasses Gaussian-Bessel methods by 38-fold while decoupling efficient thermal management from photochemical processes.

Monitoring local luminescence properties in 3D multi-scale architecture having sub-wavelength dimensions is attractive for multiple potential applications for sensors, optical data storage, integrated light source, or data communication. For such a challenge, Femtosecond (fs) Direct Laser Writing (DLW) stands out as an unique technique to imprint i...

A novel type of waveguide Bragg grating (WBG) is demonstrated based on femtosecond laser-induced Type A refractive index modifications, namely based of the photochemistry of silver species in a specialty ortho-phosphate glass matrix. First-order WBGs are reported in the near-infrared and down to 736 nm in the visible. Relative transmission measurem...

To our knowledge, we report on the first demonstration of Type A VBGs inscribed in silver-containing phosphate glasses by femtosecond laser writing. The gratings are inscribed plane-by-plane by scanning the voxel of a 1030 nm Gaussian-Bessel inscription beam. This results in a refractive-index modification zone, induced by the appearance of silver...

The femtosecond direct laser writing technique provides a robust and efficient way to directly inscribe embedded 3D photonic devices in bulk glasses. Following direct laser writing, a local optical properties change is induced that is generally classified under three distinguished types (type I, type II, and type III). Each type allows for the fabr...

In the present work, the effect of electron irradiations on silver-containing phosphate glasses using a 2.5 MeV electron beam has been explored by Electron Spin Resonance (ESR) and luminescence spectroscopy. The process involved in the interaction of electron beam with both the silver-containing and silver-free phosphate glass matrix and the format...

We report the fluorescent properties of 3D localized structure with size near the diffraction limit induced by femtosecond direct laser writing (DLW) in Yb³⁺ and silver-containing phosphate glass. The homogenous dispersion of the silver ions and Yb³⁺ ions in the glass matrix before DLW was evidenced using photo-luminescent spectroscopy and time-res...

This article deals with a general description of Angular Quasi-Phase-Matching (AQPM) in uniaxial and biaxial crystals for second-order nonlinear optical interactions. Such an exhaustive and generalized angular-dependent approach of AQPM reveals new directions of propagation with efficient parametric frequency conversion. These AQPM solutions are st...

The direct laser writing (DLW) using femtosecond lasers allows for the inscription of 3D microstructures embedded inside optical materials. Based solely on the silver ions photochemistry, the DLW in silver‐containing glasses enables to locally induce inside glasses a unique combination of optical properties. The physical modifications of the materi...

The focusing of femtosecond laser pulses is an efficient and robust way to fabricate integrated optical components in glasses. However, the induced refractive index changes are weak if compared with those obtained in lithography. Several solutions have been found to overcome such problem, the multi-scan technique being one of these. The present wor...

Radio-photoluminescence in silver-doped phosphate glasses has been extensively used for X-ray dosimetry. In this paper, we present the potential of silver clusters for X-ray spatially resolved dosimetry. Those clusters are generated in phosphate glasses containing a high concentration of silver oxide by femtosecond direct laser writing technique. T...

The structure and crystallization of silver-doped germano-gallate glasses for substitution of potassium for barium ions have been investigated. By means of Raman spectroscopy, a structural study has been carried out revealing a glass network depolymerization with the formation of non-bridging oxygens likely localized on germanium tetrahedra when th...

The ability to produce robust fiber-based integrated optical systems operating over a wide spectral domain (UV to mid-infrared), is one of today’s key challenges in photonics. This work reports on the production of crystal-free, light guiding fibers from rich Ga2O3 oxide-based glass compositions. These materials show optical transmission extending...

Volume Bragg Gratings (VBG) are inscribed in the bulk of non-conventional photosensitive glasses tailored with silver by means of femtosecond laser irradiation. Thanks to intrinsic features of the spatial distribution of silver-sustained inscribed structures, it is possible to fabricate gratings with sub-wavelength periodic refractive index modulat...

The development of coherent sources and other optical components for the mid-infrared has been hampered by the lack of sturdy materials that can withstand high power radiation or exposition to harsh environment. BGG glasses are robust materials transmitting over the 2.5–5 μm region. We report here the direct femtosecond laser fabrication of efficie...

We report on the 3D precipitation, using a direct laser writing approach, of highly fluorescent silver clusters in a Eu3+-doped silver-containing zinc phosphate glass. Micro-spectroscopy of fluorescence emission shows the ability to continuously adjust the local tri-chromatic coordinates in the CIE (Commission Internationale de l’Éclairage) chromat...

Quantitative phase imaging has been widely exploited and developed during the last decade. This technique is efficient, allowing for quantitative and qualitative spatially resolved measurements of the refractive index profiles. However, there are some measurement limitations for thick samples when exceeding the depth of field-of-view of the imaging...

Five-dimensional (5D) recording and decoding is demonstrated by using femtosecond direct laser writing in a silver-containing commercial glass. In particular, laser intensities and ellipse orientations generated by anamorphic focusing are employed to produce 5D data storage unit (3D for XYZ, 1D for the orientation of the elliptically-shaped data st...

We worked on a new scheme of quasi-phase matching (QPM) based on the negative first order of the spatial modulation of the sign of the second-order nonlinearity. Applying this scheme in the case of angular-QPM (AQPM) in a biaxial crystal reveals new directions of propagation for efficient parametric frequency conversion as well as “giant” spectral...

This review focuses on the radiation-induced changes in germanate and tellurite glasses. These glasses have been of great interest due to their remarkable potential for photonics, in terms of extended transmission window in the mid-infrared, ability of rare-earth loading suitable with a laser, and amplification in the near- and mid-infrared or high...

We study the angular dependence in polarized light of the optical absorption for the Er3+ transition 4I15∕2→4I13∕2 in Y2SiO5, revealing thus the associated anisotropy and the orientation of the related absorption principal directions in the dielectric plan perpendicular to the monoclinic axis b. The measurements are performed at low temperature. Th...

We study the angular dependence in polarized light of the optical absorption for the \er transition $^{4}I_{15/2} \rightarrow $$^{4}I_{13/2}$ in Y$_2$SiO$_5$, revealing thus the associated anisotropy and the orientation of the related absorption principal directions in the dielectric plan perpendicular to the monoclinic axis b. The measurements are...

Calcium Fluoride (CaF2) was selected owing to its cubic symmetry and excellent luminescence properties as a crystal of interest, and ultrafast laser inscription of in-bulk double-track waveguides was realized. The guiding properties of these waveguides in relation to the writing energy of the femtosecond pulse are presented. The modified double-tra...

Using femtosecond laser writing technique, near-surface waveguides with no need for additional processing were written in silver-containing glasses. An ultra-sensitive refractive index sensor exhibiting a novel double-wing feature is manufactured in a 1 cm glass chip.

We propose a new scheme of quasi-phase matching based on the negative first-order of the spatial modulation of the sign of the second-order optical nonlinearity. The experimental validation is done in a periodically-poled Rubidium-doped KTiOPO4 crystal.

Femtosecond laser writing of optical waveguides and components in glasses has been a remarkably growing research field during the last two decades. However, such laser- inscribed optical components were mostly written within the volume of the glass due to the unavoidable ablation that arises when the focal spot is approaching the glass surface. Thi...

The generation of silver species has been investigated in silver‐containing sodo‐gallo‐phosphate glasses subjected to X‐ray irradiations. Radioluminescence spectroscopy has evidenced the presence of isolated and paired silver ions. The proportion of silver pairing is found dominant in ortho‐phosphate glass compositions, compared to poly‐phosphate c...

Here, we report the luminescence properties of Yb3+/Pr3+ dual-doped fluorophosphate glasses containing silver clusters. Through the solubility of silver into the glass system as function of its initial concentration, charged species characterized as Ag+ and Agmn+ were formed and identified according to their absorption and emission spectral respons...

The femtosecond direct laser writing technique in glasses has been widely used and extensively studied during the last two decades. This technique provides a robust and efficient way to directly inscribe embedded 3D photonic devices in bulk glasses. Following direct laser writing, a local refractive index change (Δn) is induced that is generally cl...

Silver-containing glasses are promising candidates for photonic applications, due to the potentiality of spec-troscopic properties of silver nanoclusters (NC's) and/or silver metallic nanoparticles. In this framework, silver-containing fluorophosphate glasses are candidates with a strong potential. Indeed, combined with femtosecond laser irradiatio...

Femtosecond laser-induced spatial redistribution of silver species (ions, clusters, and hole centers) in a silver-containing phosphate glass is investigated by correlative means of near-field scanning optical microscopy (NSOM) images, numerical simulations, chemical micro-probe analysis, and nanoscale spatial profiles after soft etching. In particu...

Direct laser writing (DLW) of 3D embedded waveguides in glasses has been well established this last decade. However, few works of DLW of waveguides neighboring the glass surface were presented due to the ablation problems when getting near the glass surface. Some solutions have been presented like using reinforced glasses or using additional proces...

In the two last decades, development of more reliable femtosecond lasers has led to innovative laser/matter processes and key enabling technologies. Mainly applied to silica glass fibers, Direct Laser Writing (DLW) using femtosecond laser has been carried out to perform glass network photostructuration leading to many applications, including lab-in...

Silver containing glasses in the P2O5 - Ga2O3 - Na2O ternary diagram have been investigated to relate the effect of glass network structure and sodium ions concentration to spectroscopic and laser-writing properties of the materials. The first and most striking evidence is the large gain in the photosensitivity of fluorescent molecular silver clust...

Laser-induced glass processing has led to huge progress and applications over the last two decades. Here, we review recent advances in femtosecond laser-induced photochemistry in isotropic transparent oxide glasses specifically tailored with silver photoactive agents. The understanding of the influence of the considered glass matrix on the nature a...

Calcium Fluoride (CaF2) was identified among the first host crystals for active laser media. However, due to the need of charge compensation of Nd3+-doped fluorite crystal structures, other host materials like YAG, oxide and fluorite glasses were preferred over the years. Recent developments made on ytterbium-doped alkaline-earth fluorides have sho...

Direct laser writing in glasses triggers three different type of refractive index changes classified as three types (Type I, II & III). In silver containing glasses, a novel type of refractive index change called type A has been reported allowing the creation of novel type of waveguides. Type I & Type A refractive index changes both could be trigge...

We measured broad tunable spectra between 1.4 and 4.7 μm in the nonlinear crystal La3Ga5.5Ta0.5O14 (LGT). They were generated in the femtosecond regime from phase-matched difference frequency generation and optical parametric amplification.

Direct Laser writing in silver containing phosphate glasses allows fabricating multi-scale photonic structures with various optical contrast (linear and nonlinear). The glass matrix composition determines the resulting photo-induced structures.

Direct laser writing in glasses is a growing field of research in photonics since it provides a robust and efficient way to directly address 3D material structuring. Generally, direct laser writing in glasses induces physical modifications such as refractive index changes that have been classified under three different types (Type I, II & III). In...

We demonstrate phase-matched difference frequency generation in the emerging nonlinear crystal . Tunable wavelengths between 1.4 and 4.7 μm are generated by using femtosecond sources. We also report on the measurements of the optical damage threshold in the femtosecond regime and on the nonlinear refractive index .

We detail the full characterization of the anisotropy of the absorption properties of two different Yb-doped monoclinic borate compounds under polarized light. The studied crystals are Li6(Gd)0.75Yb0.25(BO3)3 and Li6Y0.75Yb0.25(BO3)3, respectively, and were grown by the Czochralski method. We focused on the study of their absorption at the zero lin...

A detailed investigation of the photo-inscription of waveguides in barium gallo-germanate (BGG, BaO, GeO2, Ga2O3) glass is presented. Upon irradiation of BGG glass samples of different contents of germanium dioxide with a femtosecond laser pulse train, positive refractive index changes are produced over a wide range of exposure conditions. Waveguid...

We report that the shape and size of fluorescent patterns can be controlled by the focused laser intensity distribution, which depends on irradiation conditions as well as on the spin and orbital angular momenta being carried by light, inducing the formation of silver cluster patterns in a silver-containing zinc phosphate glass. In particular, we d...

The formation of both local second- and third-harmonic generations (SHG and THG) induced by a train of femtosecond laser pulses in silver-doped phosphate glasses is addressed. Based on modeling calculations, including various diffusion and kinetic processes, THG is shown to result from the formation of silver clusters. The latter organize into a ri...

We measured continuously tunable beams between 1.4 and 4.7 µm in the nonlinear crystal La3Ga5.5Ta0.5O14 (LGT) as predicted theoretically. They were generated in the femtosecond regime from difference frequency generation and optical parametric amplification.

Precipitation of silver nanoparticles (Ag-NPs) can occur in a silver-doped lanthanum borogermanate glass matrix, either under thermal annealing or femtosecond direct laser writing (DLW). Macroscopic transmission and localized µ-fluorescence emission spectra provide typical plasmon resonance behavior of Ag-NPs. Annealing leads to the spatially rando...

The formation of silver cluster structures at submicrometer spatial scales under the irradiation by high-power femtosecond laser pulses with high repetition rate was observed in various glasses containing silver ions. In order to account for the formation of these structures in metal-doped glasses, we present a theoretical model for the organizatio...

In this article, we have focused our attention on the femtosecond laser irradiation of fused silica to study the mechanisms of micro-cavities and nanofibers formation. The nanofibers formed have small diameters and are extremely long, with a typical aspect ratio of 1000. Structural rearrangements and density variation have been studied by micro-Ram...

Femtosecond direct laser writing in silver-containing phosphate glasses allows for the three-dimensional (3D) implementation of complex photonic structures. Sample translation along or perpendicular to the direction of the beam propagation has been performed, which led to the permanent formation of fluorescent structures, either corresponding to a...

Tailored silver-containing zinc-phosphate glasses possess excellent thermoviscous ability and optical properties. Beyond they have proven to form a favorable matrix for the direct laser writing of photoluminescent and nonlinear patterns. Here, bringing together the merits of these materials with fiber optic technology, the first photosensitive, pho...

We report on the absorption profile of the monoclinic holmium-doped \(\hbox {KY}(\hbox {WO}_4)_2\) crystal near the optic axis for the maximal absorption wavelength at 1960 nm. The full angular distribution of the absorption coefficient at the vicinity of such optical singularity has been experimentally and numerically investigated. Furthermore, la...

We report on dual-color control of femtosecond direct laser writing (DLW) in a noncommercial silver-containing zinc phosphate glass, thanks to an additional illumination with a cw (continuous wave) UV laser, either after the femtosecond irradiation or simultaneously. By tuning the cw UV power, we demonstrate the tunable control and inhibition of th...

Optical materials can be structured by laser pulses to get new material functionalities in various scientific area going from photonics to medicine. For instance, wave guides, nano-gratings, emergence of nonlinear optical properties for data storage [1], cutting and welding of materials are applications of great interest. Structuration driven by a...

The interest to the detailed formation of silver nanostructures inside our optimized non-commercial phosphate glass occurs because of the possibility to create compact optical data storage using the fluorescence signal from laser-induced silver clusters. In this work a model and the associated numerical simulation of silver nanostructure formation...

We report on the significant role of silver ions during femtosecond laser-induced formation of nanogratings (NGs) at the surface of high optical quality gallophosphate glasses that we develop. Compared to the non-doped glass matrix, the silver-containing glass showed remarkable silver-dependent behaviors, namely lower fluence thresholds of NGs form...

We report on structured light-induced femtosecond direct laser writing (DLW) under tight focusing in non-commercial silver-containing zinc phosphate glass, which leads to original patterns of fluorescent silver clusters. These fluorescence topologies show unique features of frustrated diffusion of charged species, giving rise to distorted silver cl...

We report a method based on Malus law to directly measure the dielectric frame orientation of monoclinic crystals with an accuracy of 0.3°. This technique was validated by the study of Nd3+:YCa4O(BO3)3, Sn2P2S6, BiB3O6 and Eu3+:Y2SiO5.

Three-dimensional patterning of metal–dielectric composites is achieved at the sub-micrometer scale in glass. A high silver-content zinc-phosphate optical transparent glass is structured by means of a near-infrared femtosecond laser via non-linear absorption processes. The silver ions embedded in glass photochemically react under controlled laser i...